In recent years, a centrifugal blood pump apparatus in which driving torque from an external motor is transmitted to an impeller in a blood chamber through magnetic coupling has increasingly been used as a blood circulation apparatus of an artificial heart-lung machine. According to such a centrifugal blood pump apparatus, physical contact between the blood chamber and the outside can be eliminated, thus preventing invasion of bacteria and the like into blood.
A centrifugal blood pump in Japanese Patent Laying-Open No. 2004-209240 (PTL 1) includes a housing having first to third chambers partitioned from one another by first and second diaphragms, an impeller rotatably provided in the second chamber (blood chamber), a magnetic element provided in one surface of the impeller, an electromagnet provided in the first chamber to face the one surface of the impeller, a permanent magnet provided in the other surface of the impeller, a rotor and a motor provided in the third chamber, and a permanent magnet provided in the rotor to face the other surface of the impeller. A groove for hydrodynamic bearing is formed in a surface of the second diaphragm facing the other surface of the impeller. Owing to attractive force acting on the one surface of the impeller from the electromagnet, attractive force acting on the other surface of the impeller from the permanent magnet in the rotor, and a hydrodynamic bearing effect of the grooves for hydrodynamic bearing, the impeller moves away from an inner surface of the second chamber and rotates without contacting.
A centrifugal blood pump in Japanese Patent Laying-Open No. 2006-167173 (PTL 2) includes a housing having first to third chambers partitioned from one another by first and second diaphragms, an impeller rotatably provided in the second chamber (blood chamber), a magnetic element provided in one surface of the impeller, a first permanent magnet provided in the first chamber to face the one surface of the impeller, a second permanent magnet provided in the other surface of the impeller, a rotor and a motor provided in the third chamber, and a third permanent magnet provided in the rotor to face the other surface of the impeller. A first hydrodynamic bearing is formed in a surface of the first diaphragm facing the one surface of the impeller, and a second groove for hydrodynamic bearing is formed in a surface of the second diaphragm facing the other surface of the impeller. Owing to attractive force acting on the one surface of the impeller from the first permanent magnet, attractive force acting on the other surface of the impeller from the third permanent magnet in the rotor, and a hydrodynamic bearing effect of the first and second grooves for hydrodynamic bearing, the impeller moves away from an inner surface of the second chamber and rotates without contacting.
A turbo-type pump in FIGS. 8 and 9 of Japanese Patent Laying-Open No. 4-91396 (PTL 3) includes a housing, an impeller rotatably provided in the housing, a first permanent magnet provided in one surface of the impeller, a rotor provided outside the housing, a second permanent magnet provided in the rotor to face the one surface of the impeller, a third permanent magnet provided in the other surface of the impeller, and a magnetic element provided in the housing to face the other surface of the impeller. A first groove for hydrodynamic bearing is formed in the one surface of the impeller, and a second groove for hydrodynamic bearing is formed in the other surface of the impeller. Owing to attractive force acting on the one surface of the impeller from the second permanent magnet in the rotor, attractive force acting on the other surface of the impeller from the magnetic element in the housing, and a hydrodynamic bearing effect of the first and second grooves for hydrodynamic bearing, the impeller moves away from an inner surface of the housing and rotates without contacting.
A clean pump in Japanese Utility Model Laying-Open No. 6-53790 (PTL 4) includes a casing, an impeller rotatably provided in the casing, a first permanent magnet provided in one surface of the impeller, a rotor provided outside the casing, a second permanent magnet provided in the rotor to face the one surface of the impeller, a magnetic element provided in the other surface of the impeller, and an electromagnet provided outside a housing to face the other surface of the impeller. A groove for hydrodynamic bearing is formed in the one surface of the impeller.
The electromagnet is actuated when a rotation speed of the impeller is lower than a prescribed rotation speed, and power supply to the electromagnet is stopped when the rotation speed of the impeller becomes higher than the prescribed rotation speed. Owing to attractive force acting on the one surface of the impeller from the second permanent magnet in the rotor and a hydrodynamic bearing effect of the groove for hydrodynamic bearing, the impeller moves away from an inner surface of the housing and rotates without contacting.
Furthermore, in a centrifugal blood pump in Japanese Patent Laying-Open No. 2007-89972 (PTL 5), a rotation centerline of a rotor is arranged at a position different from that of a centerline of a second chamber such that a rotation centerline of an impeller matches the centerline of the second chamber during rotation of the impeller in the centrifugal blood pump in PTL 2.